This invention relates to a photosensor block suitable for use, for example, with a zero track sensor of a disk drive unit, and more particularly to a photosensor block which includes a photosensor mounted for adjustment thereon.
Generally, a photosensor is employed in a control device which includes a stepping motor for controlling a position of a moving body. Such a photosensor normally includes a light emitting element and a light receiving element arranged in an opposing relationship with slits located intermediately and parallelly between the elements for detecting a position of a body as the body interrupts a path of a light beam through the slits.
One of devices which incorporate a moving mechanism including a stepping motor therein is a disk drive unit such as, for example, a disk drive unit illustrated in FIG. 16. Referring to FIG. 16, a disk drive unit includes as principal components a frame 51, a holder 52 located on the frame 51, a loading member 54 for loading a cartridge 53 inserted into the holder 52 onto a turntable and for ejecting it therefrom, a carriage 56 including a magnetic head not shown for effecting recording on and reproduction from a disk 55 contained in the cartridge 53, and a stepping motor 57 for feeding the carriage 56 in a radial direction of the disk 55. A photosensor 58 is located at a portion of the frame 51 behind the carriage 56, and a shutter member 59 is mounted to extend from a rear end of the carriage 56 and is so positioned to move across a gap 60 between slits formed in an opening relationship in the photosensor 58. Since the shutter member 59 is securely mounted on the carriage 56, it moves together with the carriage 56. Accordingly, if the shutter member 59 and the photosensor 58 are positioned relative to each other such that a path of a light beam from a light emitting element to a light emitting element of the photosensor 58 is interrupted by the shutter member 59 when the magnetic head is positioned for the zero track of the disk 55, the position of the magnetic head for the zero track can be detected.
As described above, the photosensor 58 is securely mounted on the frame 51, but it is necessary to effect adjustment to obtain accurate zero track positioning when the photosensor 58 is assembled. Normally, the adjustment is such that the shutter member 59 is positioned to the zero track position and then the photosensor 58 is slightly moved to a position in which the shutter member 59 interrupts a path of a light beam whereafter it is secured to the position by means of a bolt. However, according to such an adjusting process, adjustment of the photosensor 58 is difficult and the photosensor 58 may be brought out of position upon fastening with a bolt, and hence much time is required for such adjustment.